Saturday, March 17, 2012

It has been a while... which isn't to say I haven't been running to a myriad of issues, but I just haven't had the time to update. But this one, egads. I could not help but describe and hopefully save someone out there in the interwebs many hours and tears.

Our adventure today begins with a seemingly simple task. Upgrading the Grails version for a project. The project was previously on Grails 1.3.7, and we are upgrading/updating/whichever it to 2.0. For a point of reference, here is the setup/environment :

This a fairly large code base containing many other modules.

We are using maven

My IDE of choice is Eclipse Helios (64bit)

We have a 'local' nexus that proxies stuff for us

In addition to the base Grails, we have the following plugins installed:

Spring-Security-Core

Spring-Security-Ui

Mail

JQuery

JQuery-ui

famfamfam

tomcat

hibernate

jaxrs

And we also have the following dependencies:

Spring-Security-Core

Spring-Security-Web

Note that there are two separate Spring-Security-Core, one is a plugin and one is a dependency to be added in the pom.xml. Another note, it has been many months since we set up our Grails project, and my memory just isn't what it used to be.

Here's an overview of what this blog entails:

Where are the jars?

Multiple versions of grails in the same workspace

Wait, I need to INSTALL grails as well??

Grails "upgrade" command doesn't work with maven-ized projects

Trouble re-installing the JAXRS plugin

Some final thoughts

Issue #1 - Where are the jars?
My first problem will probably be moot for most people now. I could not get the updated jars from our local nexus. It took a little searching and I came across this: Grail 2.0 jars not available through maven central. Which of course explains why our nexus didn't pull it in. The reason this is moot now is that Grails 2.0.1is available through maven central. So I was able to grab the jars for 2.0.1 fine. But for future reference, if you experience trouble pulling in the jars for new versions of Grails ... check to see if they even exist in your nexus or maven central. If not, you can grab them from Grails' repo: http://repo.grails.org/grails/core.

Issue #2 - Multiple versions of grails in the same workspace.
Since this is a major release of Grails, there are many things that have been changed and therefore our code needs to be changed to work with the Grails. Grails does provide a nice* write-up of how to upgrade your code here: Upgrading From Previous Versions of Grails.

*Since I have only just resolved my issues with getting started, I haven't yet had a chance to follow their write-up, but at a glance, it looks fairly detailed. Whether or not it is detailed enough, I will find out soon.

Because this is potentially going to perturb our code base with all the changes, I am working the upgrade in a branch that contains only this module. Seems like a sound plan, right? At this moment, I have our entire code base open in eclipse and I have this branch open. As soon as I change the POM to reference 2.0.1, and eclipse does its auto build thing to pick up this change ... the bad thing happens. Namely, eclipse exits all by it's lonesome, with no message or anything. Just, one minute it's building ... next minute it's gone.

What happened? Since I'm on a Mac, I opened up the console to take a look at what it says.. and it says a lot:

It took me quite a lot of frustration, many hours, to realize that the problem was that because the two versions of grails is so different, they can not coexist happily, at least not without some tweaking. There is a nice little script available here that does the switching automagically based on what version of grails your project needs. You only need to a little bit of setup, namely setting an environment variable to point to a default version of grails, and to have both versions of grails in the same folder. For example, this is what I did:

I decided to use 1.3.7 as my default, so I set my $GRAILS_HOME to point to that in my ~/.bashrc file:

I put the script in it's own folder (multi-grails) in the same folder with the grails version and added that information to the $PATH environment variable in the ~/.bashrc file:

(Listing 4)

export PATH=/opt/multi-grails/:$PATH

Maybe this is obvious to more experienced developers, but I've never had this problem before and I know I've worked with multiple versions of libraries opened in the same workspace before. Well, as it turns out ... this is because of my next issue.

Issue #2a - Wait, I need to INSTALL grails as well??
This is a painful thing for me to admit, and maybe it's obvious in the documentation on grails and I was just trying to do things too quickly and didn't notice. But I completely forgot I had installed grails on my machine. I just assumed it was a plugin like any other. No, no, no. You need to install grails. And by install grails, I mean:

Download the binary zip of the version you want (http://grails.org/Download)

Alright, now that I can actually VIEW my code in eclipse, I can start the upgrading process. Grails provides a nice "upgrade" command to make life easier. It is simply "upgrade". To use this command on the command line with the mavenized grails commands:

(Listing 5)

mvn grails:exec -Dcommand=upgrade

Simple, right? Ah, but no. Again, that would be too easy. What you end up with if you try this on the command line is something along the lines of, after lots of downloading of whatever other dependencies your project has:

If you look at the end of line 17 above, you can see it is looking for: /blah/blah/null/src/war. What the heck, why is it looking for null, and where did that even get specified? According to this blog, there is some problem with resolving the environment path and maven and grails. Long story short, it doesn't work. You can't (at this time at least) use the upgrade grails command on a maven-ized project.

So now what? Now you do the upgrade manually. The above mentioned blog entry has instructions as well. Here is what I did, in a little bit more detail. Note that some of the steps I'm not sure are 100% necessary, but I was getting tired of eclipse choking on me.

Exit eclipse.

Navigate to the directory of your project

Using your favorite text editor, manually edit the pom.xml file to change the grails version to 2.0.1. Note that in our case, we have declared a property at the top of the pom.xml that is used in all the grails related dependencies for consistency.

Using your favorite text editor, manually edit the application.properties to change the app.grails.version to 2.0.1.

Make a note of all the plugins that are listed in the application.properties file. For example, here are the plugins that our module uses:

As I mentioned earlier, it has been a while since we first set this up, so I didn't even remember all the plugins we were using.

Using the command line, uninstall each of these plugins. The name of the plugin to pass in for the command is what appears after the '.' in your list.

(Listing 8)

mvn grails:exec -Dcommand="uninstall-plugin" -Dargs="famfamfam"

Now, install the very same plugins, this time the install will pull in the updated versions of your plugins.

(Listing 9)

mvn grails:exec -Dcommand="uninstall-plugin" -Dargs="famfamfam"

Issue #4 - Trouble re-installing the JAXRS plugin
One of the plugins that we use is jaxrs ...which has a dependency on some restlet.org packages. For some odd reason, when trying to re-install the plugin, I keep getting errors about inability to resolve the dependency. As it turns out, the restlet version that is needed by the plugin is NOT in maven central. To fix this, I added a repository to the pom.xml(Listing 10)

restlet.orgrestlet.orghttp://maven.restlet.org

Some final thoughts ... for now...
At this point, you should be able to do a mvn clean install on your command line for the project and open both projects up in Eclipse without eclipse having a heart attack and falling over. Keep in mind that your mvn clean installwill fail, since you haven't yet changed your code to adhere to the new 2.0.1 ways. This is far as I was able to get to:

Another thing to mention is be wary of messing around with your maven-ized pom.xml file. If I remember correctly, you had to issue a specific command to turn the grails project into a maven-ized one and that the command also created/edited the pom.xml file. One of the motivating factors for us to upgrade is that we have been seeing our CI builds hang for no explicit reason when building this specific project.. Where it hangs varies, but it seems to be hanging while trying to resolve dependencies (another long story, maybe for another time). I tried to do some "cleverness" by cleaning up what I thought were now obsolete/unused dependencies ... which I should have known better than to do.

I hope this has been helpful for someone out there. I tried to document this as best as I could, but it was a long, frustrating process. I may have missed some steps, if I did and it's causing you issues, please let me know and I'll try to help out.

3 comments:

I support a similar mavenized grails app, in our case we first upgraded grails following those docs you mention, and then just changed the grails version in the pom file, but then got stuck as well trying to find the grails 2 jars in some repo. Finally also found the info that there actually is a version 2.0.1 of the grails-maven plugin and corresponding grail jars (except grails-gorm, can't find a version newer than 1.3.7), but now reached the same point of teh error "Provider for javax.xml.parsers.SAXParserFactory cannot be found". Was wondering whether you have passed that stage?Cheers,Raf.

About Me

I know a little bit about a lot of different programming languages and stuff, but sometimes, I don't know enough and find myself searching the interweb in circles for what should be a simple answer. This is a compilation of the fruits of these searches in hopes that will help some one out there that has similar questions/issues/problems and maybe save them a little bit of time. :)